1. Field of the Invention
The invention relates to a method for forming images, a method for testing an electronic device and a test system.
2. Description of the Related Art
The testing of an electronic device is very important before it is delivered for sale. The idea of testing is to ensure that an electronic device, such as a mobile phone, is in perfect working order and structurally faultless. During testing, the electronic device under test can be transferred into a test chamber through a door opening to be connected to a fixture thereof that holds the electronic device under test in position and operates as a user interface for the electronic device. The electronic device is controlled through the fixture and measurement signals are transferred from the electronic device to signal processing equipment.
The fixture may comprise sensors or actuators or the like that allow carrying out various tests. At the end of a test sequence the electronic device, which has undergone testing, is transferred from the test chamber through the door opening and a new electronic device under test is admitted to the test chamber.
What can be tested in an electronic device comprising a camera is the optical properties thereof. Thus the camera may be used to take a test image, which is stored in an image element. The image element is placed at a focusing distance of the camera in order to accurately succeed with the imaging. The shortest faithfully focusing distance from the image element to the camera that does not include an image focusing mechanism may range for instance from 0.5 m to 1.5 m. Such a significant distance between the test image and the camera is very inconvenient especially when manufacturing the device. In addition, owing to the significant distance the test image must be large in order to fill the entire image area of the camera.
A camera provided with a focusing mechanism may also be used to focus a test image nearby, but the focusing always requires a focusing operation as well as time. On the other hand a camera provided with a focusing mechanism is unable to focus at such a short distance as the testing requires, since in a compact test situation the image element cannot typically be placed further than a couple of centimeters from the camera.